I've been using the following formula for the reciprocity and it has been pretty good...

Time_new = (Time_old+1)^1.25 - 1 where "^" means "raise to the power of", probably the y_superscript_x key on most calculators.

This is Mr. Schwartzchild's formula with p=0.8

Cool! I exported a chart from Pinhole Designer and used that, but I got the impression it was over-compensating the Delta 100. Of course it was the sort of day that varied from cloudy sprinkles to sunshine and back again in five minutes, so long exposures were subject to pretty high error rates. (But they worked in spite of it all.)

I'm using portra 400vc and am getting good results. Kodak claims that there isn't any reciprocity problems until you hit the 10 second mark, and I think that seems about right. I've shot some, and if I can ever get my internet connection to work, I'll put some up at my website...